How to use typeof in js

typeof operator returns the type of operand, its syntax is: typeof operand. It returns one of the following string types: "undefined", "null", "boolean", "number", "bigint", "string", "symbol", or "object". Returning null "object" is a historical issue. Composite data structure

Usage of typeof operator in JavaScript

# The ##typeof operator is a unary operator that returns a string indicating the type of the operand.

Syntax:

<code>typeof operand</code>

Parameters:

• operand: To determine its type expression or variable.

Return value:

A string representing the type of

operand:

• "undefined": The value is undefined.
• "null": The value is null.
• "boolean": The value is a Boolean value.
• "number": The value is a number.
• "bigint": The value is a big integer.
• "string": The value is a string.
• "symbol": The value is a Symbol value.
• "object": The value is an object, including functions, arrays and regular expressions.

Example:

<code class="js">console.log(typeof undefined); // "undefined"
console.log(typeof null); // "object"
console.log(typeof true); // "boolean"
console.log(typeof 123); // "number"
console.log(typeof "Hello World"); // "string"
console.log(typeof Symbol("Symbol")); // "symbol"
console.log(typeof [1, 2, 3]); // "object"
console.log(typeof function() {}); // "function"</code>

Note: The

typeof operator only returns JavaScript primitive types The name, not the type of the custom object.
• null Returning "object" is a historical issue. It should return "null", but this cannot be changed due to backward compatibility.
If
• operand is a composite data structure, such as an array or object, the typeof operator will return "object".
The typeof operator can be used to determine whether a variable has been declared, even if it has not been assigned a value.

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